feat: add test for open

[jsjoeio]

This PR adds a test for open.

Related to #5153

[github-actions]

✨ code-server docs for PR #5256 is ready! It will be updated on every commit.

• Host: https://coder.com/docs/code-server/e715398
• Last deploy status: success
• Commit: 71689b4
• Workflow status: https://github.com/coder/code-server/actions/runs/2491115011

[codecov]

Codecov Report

Merging #5256 (71689b4) into main (744b301) will increase coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #5256      +/-   ##
==========================================
+ Coverage   72.00%   72.12%   +0.11%     
==========================================
  Files          30       30              
  Lines        1668     1668              
  Branches      367      367              
==========================================
+ Hits         1201     1203       +2     
+ Misses        400      399       -1     
+ Partials       67       66       -1     

Impacted Files	Coverage Δ
src/node/util.ts	88.57% <0.00%> (+1.14%)	⬆️

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[github-actions]

✨ code-server dev build published to npm for PR #5256!

• Last publish status: success
• Commit: 71689b4

To install in a local project, run:

npm install @coder/code-server-pr@5256

To install globally, run:

npm install -g @coder/code-server-pr@5256